Convert `kerning_table` and `variant_tables` to an array

[cbreeden]

We would be better of using a binary search for these two tables instead of a hashmap, since they are so small.

Notice the compile size of each module

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rw-r--r-- 0/0 126672 Jan  1 01:00 1970 rex-43e78ccd3d61ee32.rex-font-kerning_table.o
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